CN114786961A

CN114786961A - Metal reinforcing cord for tyres for vehicle wheels

Info

Publication number: CN114786961A
Application number: CN202080085859.0A
Authority: CN
Inventors: S·阿格雷斯蒂; G·L·达吉尼; A·阿斯卡内里
Original assignee: Pirelli Tyre SpA
Current assignee: Pirelli Tyre SpA
Priority date: 2019-12-17
Filing date: 2020-12-16
Publication date: 2022-07-22
Also published as: WO2021124138A1; EP4076988A1; US20230001741A1; BR112022009757A2

Abstract

The invention relates to a metal reinforcing cord (10) for tyres for vehicle wheels, comprising at least two metal wires (11) twisted together with a predetermined twisting pitch (P). The metal reinforcing cord (10) has a part load elongation of more than 3%, preferably more than 3.5%.

Description

Metal reinforcing cord for vehicle wheel tyre

Technical Field

The present invention relates to a metal reinforcing cord for tyres for vehicle wheels.

Background

Metal reinforcing cords for tyres for vehicle wheels are described in the applicant's US2003046919 and WO2007128335 and WO 2012055677.

Disclosure of Invention

In the following, when any numerical range between a minimum value and a maximum value is mentioned, the aforementioned minimum value and maximum value are included in the aforementioned range unless explicitly stated to the contrary.

Moreover, all ranges include any combination of the maximum and minimum values described, and include any intermediate ranges, even if not explicitly specified.

Any numerical value is considered to be preceded by the term "about" and also means any numerical value that differs slightly from the numerical value described, for example, in view of the dimensional tolerances typical in the field of reference.

The following definitions apply hereinafter.

The term "equatorial plane" of the tyre is used to indicate the plane perpendicular to the axis of rotation of the tyre which divides the tyre into two symmetrical equal portions.

The terms "radial" and "axial" and the expressions "radially inner/outer" and "axially inner/outer" respectively refer to a direction substantially parallel to the equatorial plane of the tyre and a direction substantially perpendicular to the equatorial plane of the tyre, i.e. to a direction substantially perpendicular to the axis of rotation of the tyre and to a direction substantially parallel to the axis of rotation of the tyre.

The terms "circumferential" and "circumferentially" refer to the direction of toroidal extension of the tyre, i.e. the rolling direction of the tyre, which corresponds to a direction lying on a plane coinciding with or substantially parallel to the equatorial plane of the tyre.

The term "substantially axial direction" is used to indicate a direction inclined between 70 ° and 90 ° with respect to the equatorial plane of the tyre.

The term "substantially circumferential direction" is used to indicate a direction making an angle of between 0 ° and 10 ° with respect to the equatorial plane of the tyre.

The expressions "upstream" and "downstream" are used with reference to a predetermined direction and a predetermined reference. Thus, assuming a direction, for example from left to right, and a reference along the direction, a "downstream" position relative to the reference represents a position to the right of the reference, and an "upstream" position relative to the reference represents a position to the left of the reference.

The term "elastomeric material" is used to denote a material comprising a vulcanizable natural or synthetic polymer and a reinforcing filler, wherein such material is able to withstand deformation caused by forces at room temperature and after having been subjected to vulcanization, and is able to recover rapidly and powerfully substantially its original shape and size (according to the definition of the ASTM D1566-11 standard nomenclature associated with rubber) after the deforming forces are eliminated.

The term "metallic reinforcing cord" is used to indicate an element consisting of one or more elongated elements (also called "filaments") made of metallic material and possibly coated with or incorporated in a matrix of elastomeric material.

The term "split reinforcing cord" is used to indicate a reinforcing cord comprising at least one metal wire stranded together with at least one textile yarn. In the following, reference to split reinforcing cords refers in particular to reinforcing cords comprising textile yarns of low modulus, such as nylon yarns.

The term "hybrid textile reinforcing cord" is used to indicate a reinforcing cord comprising at least one textile yarn with a low modulus (for example nylon yarn) stranded together with at least one textile yarn with a high modulus (for example aramid yarn).

The term "yarn" is used to denote an elongated element consisting of an assembly of a plurality of textile filaments or fibers.

The yarn may have one or more "ends", where the term "end" is used to denote a bundle of filaments twisted together. Preferably, a single warp yarn or at least two warp yarns twisted together are provided.

The yarns may be identified by a symbol representing the textile material, the linear density of the fibers used, and the number of warp yarns forming the yarn. For example, aramid yarn (aramid) identified as Ar1672 denotes a textile yarn comprising aramid fibers having a linear density of 1670 dtex, formed by two warp yarns twisted together.

The term "strand" is used to indicate the union of at least two filaments or yarns, or of at least one filament and at least one yarn, to constitute an elongated element intended to be twisted together with at least one other elongated element to form at least a portion of a reinforcing cord.

The term "diameter" Of The reinforcing cord or filament is used to indicate The diameter measured as specified in method BISFA E10 (International Bureau For The International approval Of The Steel tire cord Testing Methods, International acquisition Methods For Testing Steel tire cord fabrics, 1995 edition).

In the case of yarns, the term "diameter" is used to denote the diameter around the ideal circumference of all filaments defining a yarn. The diameter of the yarn increases as the number of filaments and/or yarn ends increases.

The term "thread count" of a layer is used to indicate the number of reinforcing cords per unit length provided in such a layer. The wire count can be measured in cords/decimeter (number of cords per decimeter).

The term "linear density" or "count" of a cord or yarn is used to indicate the weight of the cord or yarn per unit length. Linear density can be measured in decitex (grams per 10 km length).

The term "modulus" is used to denote the ratio between load (or force) and elongation measured at any point of the load-elongation curve according to the BISFA standard. Such a curve is plotted by calculating the first derivative of the load-elongation function defining the curve described above, normalized to the linear density expressed in tex. Therefore, modulus is expressed in cN/Tex. In the load-elongation graph, the modulus is determined by the slope of the aforementioned curve relative to the horizontal axis.

The term "initial modulus" is used to indicate the modulus calculated at the origin of the load-elongation curve, i.e. the elongation equals zero.

The term "high modulus" is used to indicate an initial modulus equal to or greater than 3000 cN/Tex. The term "low modulus" is used to indicate an initial modulus of less than 3000 cN/Tex.

For the measurement of the linear density and modulus, no stranding was applied during the test phase or stranding phase, according to the test specified by BISFA, with reference to the flat filaments/yarns.

The terms "load at break" and "elongation at break" of a reinforcing cord are used to indicate the load at break and the percentage elongation, respectively, of the reinforcing cord, evaluated with the method BISFA E6 (international bureau of man-made fibers standardization, internationally recognized steel tyre cord test methods, 1995 edition).

The term "partial load elongation" of the reinforcing cord is used to indicate the difference between the percentage elongation obtained by subjecting the reinforcing cord to a traction force of 50N and the percentage elongation obtained by subjecting the reinforcing cord to a traction force of 2.5N. The part load elongation was evaluated using method BISFA E7 (International rayon Bureau of standardization, International approved Steel tire cord test method, 1995 edition).

The term "stiffness" of the reinforcing cord is used to indicate the resistance moment to bending at a predetermined angle (typically 15 °) evaluated by method BISFA E8 (international bureau for standardization of man-made fibres, internationally recognized steel tyre cord test method, 1995 edition).

The term "metal reinforcing cord with high elongation" or "HE metal reinforcing cord" is used to indicate a reinforcing cord having the following characteristics:

a) elongation at break equal to at least 3.5%, and preferably

b) The part load elongation is between 1% and 3%.

The above characteristic "a" is calculated by the method BISFA E6 (International rayon Bureau of standardization, International approved test method for steel tire cords, 1995 edition). The above characteristic "b" is calculated by the method BISFA E7 (International rayon Bureau of standardization, International approved test method for steel tire cords, 1995 edition).

The term "wire made of NT steel" (standard tensile steel) is used to indicate a wire made of carbon steel having a tensile strength of 2800 + -200 MPa, for example a tensile strength of at least 2700MPa for a wire having a diameter of 0.28 mm.

The term "wire made of HT steel" (high tensile strength steel) is used to indicate a wire made of carbon steel having a tensile strength of 3200 ± 200MPa, for example at least 3100MPa for a wire having a diameter of 0.28 mm.

The term "wire made of ST steel" (super tensile steel) is used to indicate a wire made of carbon steel having a tensile strength of 3500 ± 200MPa, for example at least 3400MPa for a wire having a diameter of 0.28 mm.

The term "wire made of UT steel" (ultra high tensile steel) is used to denote a wire made of carbon steel with a tensile strength of 3900 ± 200MPa, for example at least 3800MPa for a wire diameter of 0.28 mm.

A tolerance of ± 200MPa is indicated to include, for each type of steel, minimum and maximum tensile strength values (typically the tensile strength value is inversely proportional to the diameter of the wire) due to different wire diameters, for example for wire diameters between 0.12mm and 0.40 mm.

The term "mechanical behavior" of the reinforcing cords is used to denote the reaction force provided by the reinforcing cords when subjected to a load (or force). In the case of traction loads, such loads result in an elongation that varies according to the load quantity according to a function determined by a specific load-elongation curve. The mechanical behavior depends on the material of the filament(s) and/or yarn(s) used, the number of such filaments/yarns, their diameter or linear density and possibly the strand pitch.

The expression "unraveling" of the reinforcing cord is used to indicate the tendency of the filaments and/or yarns of the reinforcing cord to no longer remain stably woven when the reinforcing cord is cut by the cutter. The spread was evaluated by method BISFA E3 (International Bureau of standardization for rayon, International recognized method for testing steel tire cords, 1995 edition).

The term "high-performance tire" is used to indicate tires commonly used for high-performance and ultra-high-performance automobile wheels. Such tires are generally defined as "HP" or "UHP" and allow speeds in excess of 200 km/h, even in excess of 300 km/h. Examples of such tires are tires belonging to the classes "T", "U", "H", "V", "Z", "W", "Y" according to the e.t.r.t.o. (european tire and rim technical organization) standard and racing tires, in particular tires for high piston displacement four-wheel vehicles. Typically, the tyres belonging to this class have a section width equal to or greater than 185mm, preferably comprised between 195 and 385mm, more preferably comprised between 195 and 355 mm. Such tires are preferably mounted on rims having a diameter equal to or greater than 13 inches, preferably no greater than 24 inches, more preferably comprised between 16 and 23 inches. Such a tyre may also be used in vehicles other than the aforementioned automobiles, such as high-performance sport motorcycles, i.e. motorcycles capable of speeds even up to 270km/h and above. Such motorcycles fall into a category commonly identified by super sport (hyper), hyper sport (hyper), sport travel, for lower speed ratings, scooters (scooters), road endurance (road endiro), and custom motorcycles.

The term "tyre for motorcycle wheels" is used to indicate a tyre having a high curvature ratio (generally greater than 0.200) capable of reaching high camber angles when the motorcycle is cornering.

In the following, when reference is made to car tyres, it is intended both to refer to tyres for car tyres, such as the high-performance tyres defined above, and to tyres for light-load vehicles, such as trucks, minivans, campers, pick-up trucks, vehicles generally having a total mass equal to or lower than 3500Kg when fully loaded.

The term "radial carcass structure" is used to indicate a carcass structure comprising a plurality of reinforcing cords, each oriented in a direction substantially along the axial direction. Such reinforcing cords may be incorporated in a single carcass layer, or in a plurality of carcass layers (preferably two) radially juxtaposed to each other.

The term "crossed belt structure" is used to indicate a belt structure comprising a first belt layer comprising reinforcing cords substantially parallel to each other and inclined by a predetermined angle with respect to the equatorial plane of the tyre, and at least one second belt layer arranged in a radially external position with respect to the first belt layer and comprising reinforcing cords substantially parallel to each other and oriented obliquely with respect to the equatorial plane of the tyre with respect to one of the cords of the first layer.

The term "zero-degree belt layer" is used to indicate a reinforcing layer comprising at least one reinforcing cord wound on the belt structure according to a substantially circumferential winding direction.

To reduce CO₂Emission into the atmosphere, the applicant has for many years been producing tyres with low rolling resistance for automobile and motorcycle wheels. The tyre being terminated in respective crossed beltsThe bead reinforcing structures, in and/or below denoted by "chafer" and "flipper", comprise metallic reinforcing cords, comprising in particular light steel wires, for example having a diameter equal to 0.22 mm, 0.20mm or 0.175 mm.

The applicant has chosen to use steel wires in the aforesaid structural parts of the tyre reinforcing cords comprising only steel wires because steel wires have a high rigidity and excellent fatigue resistance, being able to provide the reinforcing cords and therefore the aforesaid structural parts of the tyre with a high resistance to high compression or bending stresses to which such structural parts are normally subjected during the running of the vehicle on which the tyre is mounted. Furthermore, due to the high thermal conductivity of steel, the steel wire has a high thermal stability, providing a stable mechanical behavior of the reinforcing cord even under extreme use conditions, such as typical use conditions of high performance tires.

The applicant has also observed that steel ensures good adhesion of the reinforcing cords to the surrounding elastomeric material, with consequent advantages in terms of tyre quality.

The applicant has observed, however, that in order to avoid the risk of corrosion of the steel in the event of water leaks inside the tyre, and at the same time to maximize the adhesion between the steel and the elastomeric material, it is advisable to ensure that at each cross section of the reinforcing cord, and therefore along the entire longitudinal extension of the reinforcing cord, the elastomeric material surrounds each steel filament as completely as possible. In the case of a reinforcing cord comprising a plurality of steel filaments twisted together, it may also be advisable for the elastomeric material to penetrate as much as possible into the spaces defined between the aforesaid filaments. This is to avoid having areas where the wires may contact each other, which in fact constitute areas where cracks may form due to fatigue caused by fretting, compromising the structural integrity of the tyre.

The applicant has also observed that steel wires having a low elongation at partial load are not suitable for use in tyre structural parts requiring a high elongation at partial load, such as zero-degree belts for automobile or motorcycle tyres. In such structural components, it is considered preferable to use textile reinforcing cords with a low modulus, for example reinforcing cords made of nylon, or hybrid textile reinforcing cords or split reinforcing cords in the case where a high stiffness is also required under high load (and therefore a high modulus under high load).

In particular, reference is made to hybrid textile reinforcing cords and split reinforcing cords, which make it possible to obtain the desired elongation at partial load and the desired rigidity, thanks to their characteristic "bimodal" mechanical behaviour obtained by using materials with a low modulus and materials with a high modulus. At low loads, the mechanical behaviour of the reinforcing cords is mainly determined by the reaction force provided by the low modulus material, whereas at high loads, the mechanical behaviour of the reinforcing cords is mainly determined by the reaction force provided by the high modulus material. A reinforcing cord of this type therefore has a mechanical behavior which, in the load-elongation diagram, is transformed by a curve defined by two segments separating the joint knee, in which the segment to the left of the knee (representing the elongation at partial load) has a much smaller inclination with respect to the horizontal axis than the segment to the right of the knee (representing the stiffness).

However, the applicant has observed that, unlike metal cords, textile and split reinforcing cords do not allow sufficient adhesion of the surrounding elastomeric material. Therefore, it is necessary to coat them with an adhesive substance or to subject them to a specific chemical or physical adhesive fixing treatment.

The applicant has perceived that it is desirable to use metallic reinforcing cords also in those structural components of the tyre in which textile or spliced reinforcing cords are currently used in order to be able to obtain high elongation under part load. In this case, in fact, it is also possible to obtain the desired adhesion between the reinforcing cords and the surrounding elastomeric material in the aforementioned structural component, without the need to apply an adhesive coating to the reinforcing cords or to subject them to an adhesive fixing treatment.

The applicant has also perceived that it is desirable for the aforementioned metallic reinforcing cords to also allow sufficient penetration of the elastomeric material between the various metal filaments, so as to maximize the adhesion between the reinforcing cords and the elastomeric material and avoid the risks of corrosion and fretting of the metal filaments caused by water leaks inside the tyre.

Furthermore, according to the applicant, a sufficient penetration of the elastomeric material between the wires will result in a more uniform thermodynamic and hysteresis behavior of the structural component of the tyre, reducing the risk of cracks forming inside the structural component at the transition region between the wires and the elastomeric material.

The applicant has achieved all the objects discussed above by making a metallic reinforcing cord having a partial load elongation greater than 3%, such reinforcing cord comprising at least two metallic wires twisted together at a predetermined twisting pitch.

According to the applicant, the mutual stranding of at least two metal wires provides the aforementioned reinforcing cord with a geometry suitable both to allow the desired penetration of the elastomeric material and to ensure a high elongation when the reinforcing cord is subjected to loads (even small loads).

The applicant has found that the mechanical behaviour of the aforementioned metallic reinforcing cords at low loads can be comparable to that of textile reinforcing cords with low modulus (so as to obtain the desired elongation at partial load) and at high loads (so as to obtain high stiffness). High part load elongation is the result of helical stretching defined in the metallic reinforcing cord by the stranding of the metal wires (in this case, the reinforcing cord behaves like a spring), whereas high stiffness under high load is the result of a high elastic modulus, which is a characteristic feature of metallic materials.

The elastomeric material arranged between the wires also tends to behave like a structural component of the reinforcing cord and therefore also contributes in terms of rigidity.

In practice, the metallic reinforcing cords of the invention have a "double modulus" mechanical behavior, comparable to that of typical hybrid and split textile reinforcing cords. The aforementioned metallic reinforcing cords can therefore be used in all the structural components of tyres in which they are normally used and in all the structural components of tyres in which hybrid and split textile reinforcing cords are normally used, achieving all the advantages discussed above in relation to the use of metallic reinforcing cords (in particular: fatigue resistance, thermal stability and adhesion).

Disclosure of Invention

The present invention therefore relates to a metal reinforcing cord for tyres for vehicle wheels, comprising at least two metal wires twisted together with a predetermined twisting pitch.

Preferably, the metal reinforcing cords have a part load elongation greater than 3%, more preferably greater than 3.5%, even more preferably greater than 4%.

Such metal reinforcing cords have, in addition to all the advantageous characteristics typical of metal reinforcing cords (rigidity under high load, fatigue resistance, thermal stability and adhesion to elastomeric materials), also a high permeability and a high elongation under partial load of the elastomeric material inside them.

The particular geometry (or configuration) of the metal reinforcing strands of the present invention can be selected by varying the lay pitch of the wires or the diameter of the wires, or the number of wires, depending on the particular application.

For example, by varying the twisting pitch of the wires and/or their diameter, it is possible to increase the amount of elastomeric material incorporated between the wires and to distribute the wires more uniformly in a piece of structural component of predetermined thickness, thus achieving an increased rigidity of such structural component and a better transmission of the stresses to which such structural component is subjected during use of the tire, favouring responsiveness.

Depending on the particular geometry selected, the reinforcing cords may be more suitable for some structural components of the tire than for others. For example, geometries suitable for maximizing the penetration of the rigid and/or breaking load and/or elastomeric material in the spaces defined between the various wires, or different geometries suitable for maximizing the part load elongation and/or breaking elongation may be provided.

According to the applicant, it is preferable to maximize the rigidity and/or the breaking load and/or the permeability when using metallic reinforcing cords in the crossed belt structure of tyres for vehicle wheels, or in the reinforcing structure of the beads of tyres for vehicle or motorcycle wheels (hereinafter indicated with "chafers" and "flippers"), or in the carcass structure of tyres for motorcycle wheels, and to maximize the elongation at part load and/or the elongation at break when using metallic reinforcing cords in the zero-degree belt of tyres for vehicle and motorcycle wheels.

The applicant believes that it may be advantageous to also maximise the elongation at partial load in the carcass structure of the tyre in order to increase the permeability of the elastomeric material inside the reinforcing cords.

Applicants believe, for example:

to maximize the rigidity and/or breaking load, the number and/or diameter of the wires may be increased;

to maximize the permeability, the stranding pitch of the wires can be increased while keeping the other parameters unchanged;

to maximize the part load elongation and/or the elongation at break, the stranding pitch of the wires can be reduced while keeping the other parameters unchanged.

The advantageous effect related to the high permeability of the elastomeric material between the metal filaments of the metal reinforcing cord of the present invention, and therefore to the greater uniformity of the distribution of the metal filaments in the structural component of the tyre, is that the stranding pitch of the metal filaments can be increased without the risk of unraveling occurring. This allows to achieve an increase in the number of metal reinforcing cords produced in a predetermined period of time (hereinafter, this feature is also referred to as "machine output"), with economic and production advantages.

The present invention may have at least one of the preferred features described below. Thus, these features may be provided alone or in combination with one another, unless explicitly stated otherwise.

The at least two wires may or may not have the same diameter.

Preferably, said at least two wires are made of steel. Such steel wires may or may not have the same carbon content.

Preferably, the first stranding pitch is greater than or equal to 1mm, more preferably greater than or equal to 3 mm.

Preferably, the elongation at break of the metal reinforcing cords is greater than or equal to 4.5%, more preferably greater than or equal to 6%.

In some embodiments, the at least two wires comprise at least one first wire and at least one second wire, the at least one first wire being substantially straight, the at least one second wire being wound on the at least one first wire with a winding pitch equal to the predetermined first twisting pitch.

In other embodiments, the at least two wires define at least one first strand of wires.

Preferably, the at least one first strand of wires is twisted together with the at least one second wire with a second twist pitch.

The second twist pitch may be equal to or different from the first twist pitch.

Preferably, the number of wires of the at least one first strand of wires is greater than or equal to 2.

Preferably, the number of wires of the at least one first strand of wires is less than or equal to 7.

In a preferred embodiment, the number of wires of the at least one first strand of wires is between 2 and 7.

In some embodiments, the at least one first strand of wire is stranded together with a plurality of second wires.

Preferably, the number of second wires is greater than or equal to 2.

Preferably, the number of second wires is less than or equal to 7.

In a preferred embodiment, said second number of wires is between 2 and 7.

The number of wires of the at least one first strand of wires may be equal to or different from the number of wires of the second strand of wires.

In a further embodiment, the second wire defines at least one second strand of metal twisted together at a third twist pitch.

The third twist pitch may be equal to or different from the first twist pitch.

In all of the above embodiments, the wire diameter of the at least one first strand of wire may be equal to or different from the diameter of the at least one second wire.

It is possible to actuate a solution suitable for ensuring that said at least two metal filaments are spaced apart from each other in any cross section of the metal reinforcing cord.

Such a solution preferably comprises suitably deforming (or preforming or crimping) the metallic reinforcing cords until all the metal filaments are spaced apart from each other along the entire longitudinal extension of the reinforcing cords. Such deformation (or preforming or crimping) can be obtained by passing the reinforcing cords at a predetermined tension through a plurality of cylinders having a reduced diameter (for example between 1 and 5mm) to provide metallic reinforcing cords of very high curvature.

Thus, in some embodiments, deforming the metal reinforcing cords comprises pulling said metal reinforcing cords by a constant or time-varying traction force. In this way, the relative spacing of the various wires, and thus their distribution in a predetermined sheet of the structural component of the tyre, can be adjusted as desired.

As the spacing between the various metal filaments varies, both the permeability of the elastomeric material in the metal reinforcing cord and the rigidity of the metal reinforcing cord vary.

Drawings

Further features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, with reference to the accompanying drawings.

In these figures:

FIG. 1 is a schematic partial half-section view of a portion of one possible embodiment of a tire in which a metal reinforcing cord according to the invention can be used;

fig. 2 is a photograph of a section of a first embodiment of a metal reinforcing cord according to the invention;

FIG. 3 is a photograph of a textile yarn used to make the metal reinforcing cord of FIG. 2;

FIG. 3a is a photograph of an elongated element used to manufacture the metal reinforcing cord of FIG. 2 by the textile yarns of FIG. 3;

fig. 4 is a schematic view of a first embodiment of an apparatus for manufacturing metal reinforcing cords according to the present invention, such apparatus performing a continuous process;

fig. 5a and 5b show a second embodiment of the apparatus for manufacturing metal reinforcing cords according to the present invention, such apparatus performing a discontinuous process;

6-9 show some load-elongation graphs of conventional cords and metal reinforcing cords made according to the invention;

10-19 illustrate various examples of metal reinforcing cords made in accordance with the present invention and conventional metal reinforcing cords; some cross sections of each of the aforementioned reinforcing cords in the respective elastomeric material sheet are also shown;

fig. 20 and 21 show respective segments of further embodiments of the metal reinforcing cord made according to the present invention.

Detailed Description

For the sake of simplicity, fig. 1 shows only a portion of one embodiment of a tyre 100 produced with the method and apparatus of the invention, the remaining portions, not shown, being substantially identical and symmetrically arranged with respect to the equatorial plane M-M of the tyre.

Specifically, the tire 100 shown in fig. 1 is a tire for a four-wheeled vehicle.

Preferably, tire 100 is an HP or UHP tire for sports and/or high or ultra high performance automobiles.

In FIG. 1, "a" represents the axial direction, "c" represents the radial direction, "M-M" represents the equatorial plane of the tire 100, and "R-R" represents the axis of rotation of the tire 100.

The tyre 100 comprises at least one support structure 100a and, at a radially external position with respect to the support structure 100a, a tread band 109 made of elastomeric material.

The support structure 100a comprises a carcass structure 101, the carcass structure 101 comprising at least one carcass layer 111.

In the following, for the sake of simplifying the description, reference will be made to an embodiment of the tyre 100 comprising a single carcass layer 111, however it should be understood that what is described has similar applications in tyres comprising more than one carcass layer.

The carcass layer 111 has axially opposite end edges engaged with respective annular anchoring structures 102, referred to as bead cores, possibly associated with elastomeric fillers 104. The region of tyre 100 comprising the bead cores 102 and possible elastomeric fillers 104 forms an annular reinforcing structure 103, called "bead structure", and is intended to allow anchoring of the tyre 100 on a corresponding mounting rim (not shown).

Carcass layer 111 comprises a plurality of reinforcing cords 10' coated with an elastomeric material or incorporated in a matrix of crosslinked elastomeric material.

The carcass structure 101 is of the radial type, i.e. the reinforcing cords 10' lie on a plane comprising the rotation axis R-R of the tyre 100 and substantially perpendicular to the equatorial plane M-M of the tyre 100.

Each annular reinforcing structure 103 is associated with the carcass structure 101 by folding back (or turning over) the opposite end edges of at least one carcass layer 111 around the bead cores 102 and possibly the elastomeric filler 104, so as to form a so-called turnup 101a of the carcass structure 101.

In one embodiment, the coupling between the carcass structure 101 and the annular reinforcing structures 103 can be obtained by means of a second carcass layer (not shown in fig. 1) applied in a radially external position with respect to the carcass layer 111.

A wear strip 105 is arranged at each annular reinforcing structure 103 so as to wrap around the annular reinforcing structure 103 along axially inner, axially outer and radially inner regions of the annular reinforcing structure 103, the wear strip 105 thus being arranged between the annular reinforcing structure 103 and the rim when the tyre 100 is mounted on the rim. However, embodiments are envisioned that do not provide such wear strips 105.

The support structure 100a comprises, in a radially external position with respect to the carcass structure 101, a crossed belt structure 106, which belt structure 106 comprises at least two belt layers 106a, 106b arranged radially juxtaposed with respect to each other.

The belt layers 106a, 106b include a plurality of reinforcing

cords

10a, 10b, respectively. Such reinforcing

cords

10a, 10b have an inclined orientation with respect to the circumferential direction of the tyre 100 or to the equatorial plane M-M of the tyre 100, which is comprised between 15 ° and 45 °, preferably between 20 ° and 40 °. Such an angle is for example equal to 30 °.

The support structure 100a may also comprise a further belt layer (not shown) arranged between the carcass structure 101 and the radially inner belt layer of the aforementioned belt layers 106a, 106b and comprising a plurality of reinforcing cords having an inclined orientation with respect to the circumferential direction of the tyre 100 or to the equatorial plane M-M of the tyre 100 equal to an angle of 90 °.

The support structure 100a may also comprise a further belt layer (not shown) disposed in a radially external position with respect to the radially outer belt layer of the aforementioned belt layers 106a, 106b and comprising a plurality of reinforcing cords having an inclined orientation with an angle of between 20 ° and 70 ° with respect to the circumferential direction of the tyre 100 or to the equatorial plane M-M of the tyre 100.

The reinforcing

cords

10a, 10b of the belt layers 106a, 106b are parallel to each other and have a crossed orientation with respect to the reinforcing cords of the other belt layer 106b, 106 a.

In an ultra-high performance tire, the belt structure 106 may be a reversed crossed belt structure. Such a belt structure is made by arranging at least one belt layer on the support element and turning the opposite side end edges of said at least one belt layer. Preferably, the first belt layer is initially deposited on the support element, the support element is then radially expanded, the second belt layer is then deposited on the first belt layer, and finally the opposite axial end edge of the first belt layer is turned over on the second belt layer to cover at least partially the second belt layer as the radially outermost layer. In some cases, a third belt layer may be deposited on the second belt layer. Advantageously, the turning over of the axially opposite end edges of the belt layer on the radially outer belt layer imparts greater reactivity and responsiveness to the tire as it enters a curve.

The support structure 100a comprises at least one zero-degree belt layer 106c, commonly known as "zero-degree belt", in a radially external position with respect to the crossed belt structure 106. It comprises reinforcing cords 10c oriented in a substantially circumferential direction. Such reinforcing cords 10c therefore form an angle of a few degrees (generally less than 10 °, for example between 0 ° and 6 °) with respect to the equatorial plane M-M of the tyre 100.

The tread band 109 is applied in a radially external position with respect to the zero-degree belt structure 106c, similar to the other semifinished products constituting the tyre 100.

Respective sidewalls 108 made of elastomeric material are also applied on opposite lateral surfaces of the carcass structure 101, in an axially external position with respect to the carcass structure 101 itself. Each sidewall 108 extends from one of the side edges of the tread band 109 to the respective annular reinforcing structure 103.

When the wear strips 105 are provided, the wear strips 105 extend at least to the respective side walls 108.

In some embodiments, such as those shown and described herein, the stiffness of the sidewall 108 may be increased by providing a stiffening layer 120, commonly referred to as a "steel hoop core wrap" or additional strip inserts, the stiffening layer 120 having the function of increasing the stiffness and integrity of the annular reinforcing structure 103 and the sidewall 108.

The flipper 120 is wrapped around the respective bead core 102 and elastomeric filler 104 so as to at least partially surround the annular reinforcing structure 103. In particular, the flipper 120 wraps around the annular reinforcing structure 103 along axially inner, axially outer and radially inner regions of the annular reinforcing structure 103.

The flipper 120 is disposed between the turned-over end edge of the carcass layer 111 and the corresponding annular reinforcing structure 103. Typically, the flipper 120 is in contact with the carcass layer 111 and the annular reinforcing structure 103.

In some particular embodiments, as in the embodiments shown and described herein, the bead structure 103 may also comprise a further reinforcing layer 121, generally known by the term "chafer" or protective strip, and having the function of increasing the rigidity and integrity of the annular reinforcing structure 103.

The chafers 121 are associated with respective overturning end edges of the carcass layer 111, in an axially external position with respect to the respective annular reinforcing structure 103, and extend radially towards the sidewalls 108 and the tread band 109.

The flipper 120 and the chafer 121 comprise reinforcing cords 10d (in the figures, the cords of the chafer 121 are not visible), which are coated with elastomeric material or incorporated in a matrix of cross-linked elastomeric material.

The tread band 109 has, at a radially external position thereof, a rolling surface 109a for contact with the ground. The rolling surface 109a has circumferential grooves (not shown in fig. 1) formed thereon, which are connected by transverse notches (not shown in fig. 1), thereby defining a plurality of blocks (not shown in fig. 1) of different shapes and sizes on the rolling surface 109 a.

A sublayer 107 is arranged between the zero degree belt 106c and the tread band 109.

In some particular embodiments, as in the embodiments shown and described herein, strips 110 of elastomeric material, commonly referred to as "mini-sidewalls", may be provided in the connection regions between the sidewalls 108 and the tread band 109. The mini-sidewalls 110 are generally obtained by co-extrusion with the tread band 109 and allow an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108.

Preferably, the end portions of the sidewalls 108 directly cover the lateral edges of the tread band 109.

In the case of a tire without air chambers, the layer 112 of elastomeric material, commonly called "liner", can also be arranged in a radially inner position with respect to the carcass layer 111, to provide the necessary impermeability to the inflation air of the tire 100.

Depending on the type of tyre 100, the reinforcing

cords

10a, 10b, 10c, 10d may be metal reinforcing cords 10 made according to the present invention. Such a metal reinforcing cord 10 can also be used in the carcass structure or belt structure of a tyre for motorcycle wheels.

Fig. 2 shows an embodiment of a metal reinforcing cord 10 made according to the present invention.

With reference to such a figure, the metallic reinforcing cord 10 comprises a plurality of metal wires 11 (four in the example shown), each extending along the longitudinal direction L according to a helical geometry defined by a respective helical line having a predetermined winding pitch P. Thus, the metallic reinforcing cord 10 extends longitudinally along a helical path having the aforementioned predetermined winding pitch P.

With reference to fig. 3 and 3a, the metallic reinforcing cord 10 of fig. 2 is obtained by stranding together said plurality of filaments 11 and a textile yarn 20 (for example of the type shown in fig. 3) in a conventional stranding machine (not shown in the figures), with a stranding pitch equal to the aforementioned winding pitch P, to produce an elongated element 15 (for example of the type shown in fig. 3 a).

As will be described below with reference to fig. 4 and fig. 5a, 5b, the textile yarn 20 is intended to be removed from the elongated element 15. After such removal, the metal filaments 11 maintain the aforementioned helical geometry and define the metal reinforcing cord 10, which metal reinforcing cord 10 will also have a helical geometry.

The wires 11 are preferably all made of the same material, more preferably all made of steel. The metal wire 11 may be a wire made of NT (standard tensile strength) steel or a wire made of HT (high tensile strength) steel or a wire made of ST (ultra tensile strength) steel or a wire made of UT (ultra tensile strength) steel.

The carbon content of the wire 11 is lower than or equal to 1, preferably lower than or equal to 0.9%.

Preferably, the carbon content is greater than or equal to 0.7%.

In a preferred embodiment, the carbon content is between 0.7% and 1%, preferably between 0.7% and 0.9%.

The wire 11 is typically coated with brass or another corrosion resistant coating (e.g., Zn/Mn).

The diameter of the wire 11 is preferably greater than or equal to 0.04 mm, more preferably greater than or equal to 0.08 mm, and even more preferably less than or equal to 0.10 mm.

The diameter of the wire 11 is preferably less than or equal to 0.60 mm, more preferably less than or equal to 0.45 mm.

In a preferred embodiment, the diameter of the wire 11 is between 0.04 and 0.60 mm, preferably between 0.08 and 0.45 mm, even more preferably between 0.10 and 0.45 mm.

For example, the diameter of the wire 11 is equal to 0.10 mm, or 0.12mm, or 0.13 mm, or 0.15mm, or 0.175mm, or 0.20mm, or 0.22 mm, or 0.245 mm, or 0.25 mm, or 0.265 mm, or 0.27 mm, or 0.28mm, or 0.30mm, or 0.32 mm, or 0.35 mm, or 0.38 mm, or 0.40mm, or 0.42 mm, or 0.45 mm.

Preferably, the wires 11 all have the same diameter, but embodiments are envisioned in which the wires 11 have different diameters.

The number of wires 11 is preferably between 2 and 27, more preferably between 2 and 25, even more preferably between 2 and 21.

Textile yarns 20 are preferably made of a water-soluble synthetic polymeric material, even more preferably polyvinyl alcohol (PVA). Such textile yarns 20 may be purchased from a Specialty manufacturer, such as Kuraray, Inc. or Sekisui Specialty Chemicals, or made by twisting together a plurality of PVA filaments in a conventional twisting machine.

The diameter of textile yarn 20 is preferably greater than or equal to 0.15mm, more preferably greater than or equal to 0.30 mm.

The diameter of textile yarn 20 is preferably less than or equal to 2mm, more preferably less than or equal to 1 mm.

In a preferred embodiment, the diameter of textile yarn 20 is between 0.15 and 2mm, preferably between 0.30 and 1 mm.

The linear density of textile yarn 20 is preferably greater than or equal to 200 dtex, more preferably greater than or equal to 700 dtex.

The linear density of textile yarn 20 is preferably less than or equal to 4400 dtex, more preferably less than or equal to 1670 dtex.

In a preferred embodiment, the linear density of textile yarn 20 is between 200 dtex and 4400 dtex, preferably between 700 dtex and 1670 dtex.

The elongate element 15 may comprise more than one textile yarn 20.

Each metal wire 11 may be twisted on itself in the same or opposite direction as it is twisted on textile yarn 20.

The stranding pitch P of the wires 11 is preferably greater than or equal to 2mm, more preferably greater than or equal to 3mm, even more preferably greater than or equal to 4 mm.

The stranding pitch P of the wires 11 is preferably less than or equal to 50mm, more preferably less than or equal to 25 mm.

In a preferred embodiment, the stranding pitch P of the wires 11 is between 2 and 50mm, preferably between 4 and 25 mm.

The arrangement of the metal filaments 11 around the textile yarn 20 is such that the metal filaments 11 are not completely wrapped around the textile yarn 20. In particular, the metal filaments 11 are arranged around the textile yarn 20 such that in any cross section of the elongated element 15 they are only located at angular portions around the desired circumference of the textile yarn 20. Such an angular portion is defined by an angle preferably greater than or equal to 15 °, more preferably greater than or equal to 20 °.

Preferably, the angle is less than or equal to 45 °, more preferably less than or equal to 30 °.

In a preferred embodiment, the angle is between 15 ° and 45 °, more preferably between 20 ° and 30 °.

The metal reinforcing cord 10 can be obtained from a plurality of elongated elements 15 twisted together.

The metal filaments 11 may be twisted together with the textile yarns 20 at the aforementioned twisting pitch P to form a metal reinforcing cord 10 having an n x D type configuration, where n is the number of metal filaments 11 and D is the diameter of the metal filaments 11.

Fig. 2, 11, 12, 14, 15, 16 and 19 show examples of metal reinforcing cords 10 having an n × D type configuration.

The metallic reinforcing cord 10 of fig. 2 has a 4 × D configuration, while the configurations of the reinforcing cords of fig. 11, 12, 14, 15, 16 and 19 are illustrated in the preceding figures.

Preferably, in the metallic reinforcing cord 10 having an n × D type configuration, the number of metallic filaments 11 is between 2 and 7, more preferably between 2 and 6, even more preferably between 2 and 5. Preferably, all the wires 11 have the same diameter.

Alternatively, the metal wires 11 may be twisted together at the aforementioned twisting pitch P to form the respective metal wire strands 11, and then these metal wire strands 11 are twisted together to form the metal reinforcing cord 10.

Fig. 10, 13, 17 and 18 show examples of such a metal reinforcing cord 10. Such a metal reinforcing cord 10 has a configuration of the type mxnxd, where m is the number of strands twisted together, n is the number of wires of the respective strand and D is the diameter of the latter. The construction of the reinforcing cords of fig. 10, 13, 17 and 18 is shown in the preceding figures.

In the metal reinforcing cord 10 having the m × n × D type configuration, the number of strands of the metal wires 11 may be equal to or different from the number of metal wires per strand of the metal wires 11.

Preferably, the number of strands of the wire 11 is between 3 and 6, more preferably between 2 and 5.

Preferably, the number of wires 11 per strand of wire 11 is between 2 and 7.

The stranding pitch of the wires of one wire 11 may be equal to or different from the stranding pitch of the wires of the other wire 11 and equal to or different from the stranding pitch of the respective wires 11.

Preferably, all the wires of all the wire strands 11 have the same diameter, but embodiments are foreseen in which the wires of one strand 11 have the same diameter, such a diameter being different from the diameter of the wires of the other strand 11.

Alternatively, the wires 11 may be twisted together to assume the geometry shown in fig. 20, or a different geometry as shown in fig. 21.

In the embodiment of fig. 20, the metallic reinforcing cord 10 comprises a substantially straight first wire 11a around which a second wire 11b is wound with the aforementioned twisting pitch P in a helical manner. Thus, the metal reinforcing cord of fig. 20 has a 1+1 × D configuration, where D is the diameter of the

metal filaments

11a and 11 b.

Preferably, in the metal reinforcing cord having a configuration of 1+1 × D, the

wires

11a and 11b have the same diameter, but embodiments are foreseen in which the

wires

11a and 11b have different diameters.

Further embodiments are foreseen which comprise a plurality of substantially parallel wires 11a and a wire 11b wound in a helical line on such wires 11 a. Such a metal reinforcing cord 10 has a 1+ n × D type configuration, where n is the number of wires 11a and D is the diameter of the

wires

11a and 11 b.

Preferably, in the metallic reinforcing cord 10 having a 1+ n × D type configuration, the number of metallic filaments 11a is between 2 and 7, more preferably between 2 and 6.

Preferably, the wires 11a have the same diameter, but embodiments are foreseen in which the

wires

11a and 11b have different diameters.

Alternatively, a metallic reinforcing cord 10 may be provided, this metallic reinforcing cord 10 comprising a single substantially straight metal wire 11a and a plurality of metal wires 11b wound in a helical line on the aforementioned metal wire 11 a. This metal reinforcing cord 10 has a nx1 × D type configuration, where n is the number of wires 11b and D is the diameter of the

wires

11a and 11 b.

Preferably, in the metal reinforcing cord 10 having a configuration of nx1 × D type, the number of the metal wires 11b is between 2 and 7, more preferably between 2 and 6.

Preferably, the wires 11b have the same diameter, but embodiments are envisioned in which the

wires

11a and 11b have different diameters.

In the embodiment of fig. 21, the metallic reinforcing cord 10 comprises at least two

metal wires

11a, 11b twisted together with the aforesaid twisting pitch to define at least one metal wire 11. The strand of the metal wire 11 is twisted together with a plurality of metal wires 12 (three metal wires 12 in the case shown in fig. 12), and the twisting pitch P1 may be equal to or different from the twisting pitch P (in the specific example shown in fig. 21, P1 is different from P). Such a metal reinforcing cord 10 has a configuration of the type m + n × D, where m is the number of strands of the metal wires 11, n is the number of metal wires, and D is the diameter of the

metal wires

11a and 11 b.

The metal reinforcing cord of fig. 21 has a construction 1+3 × D.

The number of wires per strand of wire 11 may be equal to or different from the number of strands of wire 11 and the number of wires 12.

Preferably, the number of wires per strand of wire 11 is between 1 and 7.

Preferably, the number of strands of the wire 11 is between 1 and 7, more preferably between 1 and 6, even more preferably between 1 and 4.

Preferably, the number of wires 12 is between 2 and 7.

Preferably, the

wires

11a, 11b and 12 all have the same diameter, but embodiments are envisaged in which the wire 12 has a different diameter than the

wires

11a, 11 b.

Referring to fig. 4, an embodiment of an apparatus for manufacturing a metal reinforcing cord 10 according to the present invention and an embodiment of a method for manufacturing a metal reinforcing cord 10 according to the present invention are described. For the sake of simplicity of description, reference will be made to a metal reinforcing cord 10 obtained from a single elongated element 15, the elongated element 15 being obtained by twisting together two metal wires 11 with a single textile yarn 20. For simplicity of illustration, only one of the two wires 11 is shown in fig. 4.

The textile yarn 20 and the metal wire 11 are taken from the respective reels 40 and 30 (the other reel 30 from which the other metal wire 11 is taken is not visible) and fed to a twisting device 60 to be twisted together, thereby forming the elongated element 15. Thus, the twisting device 60 is arranged downstream of the

reels

40 and 30 with respect to the feeding direction indicated with a in fig. 4.

The elongated element 15 is fed along said feeding direction a to a removal device 70, in which removal device 70 textile yarns 20 are removed from the elongated element 15, thereby obtaining a metal reinforcing cord 10. Thus, the removing device 70 is arranged downstream of the twisting device 60 with respect to the feeding direction a.

In a preferred embodiment of the invention, the removal device 70 comprises a hot water jet feeding device 73, which hot water jet feeding device 73 is configured to feed a jet of hot water in a counter-current manner towards the elongated element 15 when the elongated element 15 is moved along the feeding direction a. The jets of hot water dissolve the textile yarns 20 while such jets cross the metal filaments 11, which metal filaments 11 are still the only constituent elements of the metal reinforcing cord 10.

Preferably, the metallic reinforcing cord 10 thus formed then passes through a drying device 75 to be subsequently wound in a respective collection reel 50, from which collection reel 50 the metallic reinforcing cord 10 can be taken during the manufacture of the specific structural component of the tyre 100 of interest. The drying device 75 is therefore arranged downstream of the removal device 70 with respect to the feed direction a.

In the process described above with reference to fig. 4, the manufacture of the metal reinforcing cord 10 is carried out while obtaining the elongated element 15 (and while removing the textile yarns 20). The metal reinforcing cord 10 is thus made by a continuous process comprising, in chronological order without interruption or stoppage, the manufacture of the elongated element 15 by mutually twisting the metal wires 11 with the textile yarns 20, the movement of the elongated element 15 so manufactured along the feed direction a, the removal of the textile yarns 20, the possible drying of the metal reinforcing cord 10 so formed, and the winding of the metal reinforcing cord 10 in the collection reel 50.

However, the metal reinforcing cord 10 can be manufactured in two distinct operating steps, i.e. by a discontinuous process, such as the one illustrated in fig. 5a, 5 b. This process differs from the one described above with reference to figure 4 only in that the elongated element 15, once made, is collected in a service reel 45 (figure 5a), from which the elongated element 15 can be taken out when it is necessary to continue the manufacture of the metal reinforcing cord 10, as previously described (figure 5 b). Thus, when manufacturing the elongated element 15, the service reel 45 is intended to be arranged downstream of the stranding device 60, whereas when the textile yarn 20 is removed from the elongated element 15 to manufacture the metal reinforcing cord 10, the service reel 45 is intended to be arranged upstream of the removal device 70.

The metal reinforcing cords 10 are intended to be incorporated into a sheet of elastomeric material by a conventional calendering process in a conventional rubberizing machine to make the various structural components of the tire 100 described above.

The metal reinforcing cords 10 can be made in different helical geometries according to the specific application (type of tyre of interest or structural component thereof of interest). The helix geometry may be varied by intervention in one or more of the number of

wires

11, 11a, 11b, the diameter (or linear density) of textile yarns 20 (i.e. the number of filaments and/or warp yarns of textile yarns 20), the twist pitch P, the number of textile yarns 20, the degree of preforming in the twisting device 60 or the gumming machine.

According to a predetermined helical geometry, the metal reinforcing cords 10 will have different mechanical behavior, which is transformed into different curves in the load-elongation diagram. Thus, it is possible to manufacture the metal reinforcing cord 10 having different rigidity, breaking load, breaking elongation, permeability and partial load elongation.

Fig. 6 shows a qualitative example of the comparison of the mechanical behaviour of a conventional reinforcing cord with a metallic reinforcing cord 10 made according to the invention.

To the right are the load-elongation curves relative to various metal reinforcing cords produced with the method described above with reference to fig. 4, 5a and 5b and having different helical geometries.

On the other hand, on the left are shown the load-elongation curves of four conventional reinforcing cords, the curve denoted by 1 being a HE metal reinforcing cord comprising three strands of twisted together metal wires, each strand comprising three steel wires having a diameter equal to 0.20mm (such a curve therefore having a configuration identifiable as 3 x 0.20 HE), the curve denoted by 2 being a HE metal reinforcing cord comprising three strands of twisted together metal wires, each strand comprising four steel wires having a diameter equal to 0.20mm (such a curve therefore having a configuration identifiable as 3 x 4 x 0.20 HE), the curve denoted by 3 being a HE metal reinforcing cord comprising three strands of twisted together metal wires, each strand comprising 7 steel wires having a diameter equal to 0.20mm (such a curve therefore having a configuration identifiable as 3 x 7 x 0.20 HE), the curve denoted by 4 being a split reinforcing cord comprising woven yarns of Polyester (PES), the textile yarn is twisted together with three strands of metal wires, each strand comprising two steel wires having a diameter equal to 0.15mm (such a curve therefore having a configuration recognizable as PES +3 × 2 × 0.15).

Fig. 6 shows that, according to a predetermined spiral geometry (i.e. conformation), the metallic reinforcing cords have different mechanical behaviour, thus enabling to obtain a stiffness and breaking load comparable to that of conventional HE metallic reinforcing cords, the elongation at partial load and/or breaking elongation being even much greater than that of conventional HE metallic reinforcing cords and of conventional split or hybrid textile reinforcing cords.

As an example, fig. 7 shows the load-elongation curves of four metal reinforcing cords 10 made according to the invention and having different helical geometries:

-the reinforcing cord of the curve denoted by a has the configuration (32) +2 × 0.30 HT;

-the reinforcing cord of the curve denoted by b has the configuration (16) +6 × 0.14 HT;

-the reinforcing cord of the curve denoted by c has the configuration (32) +4 × 0.14 HT;

the reinforcing cord of the curve denoted by d has the configuration (32) +6 × 0.14 HT.

In the foregoing construction, the numbers in brackets indicate the number of warp yarns twisted together to obtain textile yarn 20, which textile yarn 20 will subsequently be removed (so the number indicates the diameter of the textile yarn 20), + followed by a number indicating the number of wires twisted together with the textile yarn 20, + followed by a number indicating the diameter of the wires (in mm), HT indicating the type of steel used.

Fig. 7 shows that it is possible to manufacture a metal reinforcing cord 10 with a partial load elongation even equal to 12% and an elongation at break even equal to 15%. These values are much greater than those obtainable with conventional metal reinforcing cords; in fact, in the case of HE metal reinforcing cords, the latter generally have elongation at partial load values not greater than 3% and elongation at break values not greater than 5%. It should also be noted that, for example, by increasing the number of warp yarns in textile yarn 20 (and hence the diameter of textile yarn 20) while keeping other parameters constant, the part load elongation and elongation at break are increased, thereby keeping the stiffness and load at break constant (comparison between curves b and d).

As an example, fig. 8 shows the load-elongation curves of a conventional metal reinforcing cord (curve a) and two metal reinforcing cords 10 having different helical geometries (curves B and C). The reinforcing cord of the curve denoted by a has a configuration of 3 × 4 × 0.175HE and a stranding pitch equal to 6.3mm (it is therefore a conventional HE metal reinforcing cord made by stranding together three strands of metal wires, each comprising four steel wires with a diameter equal to 0.175mm, with a stranding pitch equal to 6.3 mm). The reinforcing cord of the curve denoted by B has the configuration (36) +3 × 4 × 0.175HE and a stranding pitch equal to 6.3mm (it is therefore a HE metal reinforcing cord made by stranding together the cord as described above and a textile yarn of 36 warp yarns stranded together). The reinforcing cords of the curve denoted by C have the same construction as the reinforcing cords of the curve denoted by B, except for having a greater stranding pitch (equal to 12.5 mm).

Fig. 8 shows that the metal reinforcing cord 10 made according to the present invention has a much greater elongation at part load and elongation at break than the conventional HE metal reinforcing cord, without significant reduction in stiffness and load at break, while keeping the stranding pitch, number of wires, wire diameter and metal material constant (comparison between curves a and B). It should also be noted that the variation of the helical geometry of the metal reinforcing cord 10 obtained by increasing the stranding pitch P alone results in a reduction of the elongation at partial load and of the elongation at break, in which case the rigidity and of the load at break are also not significantly reduced with respect to those of the conventional HE metal reinforcing cords (comparison between curves B and C).

As an example, fig. 9 shows the load-elongation curves of a conventional HE metal reinforcing cord of the 3 × 7 × 0.20HE type (curve a) and four metal reinforcing cords 10 having different spiral geometries (curve B, C, D, E).

The reinforcing cord of the curve denoted by a is a conventional HE metal reinforcing cord comprising three strands of metal wires, each strand comprising seven wires having a diameter equal to 0.20mm, and the part load elongation is increased by preforming. The three strands were twisted together with a twist pitch equal to 3.15mm, while the seven wires of each strand were twisted together with a twist pitch equal to 6.3 mm. Therefore, it has a 3 × 7 × 0.20HE configuration.

The reinforcing cord of the curve indicated with B has the same configuration as described above, but it is made of an elongated element obtained by winding the aforementioned strands on a textile yarn having 18 warp yarns twisted together. Therefore, it has the (18) +3 × 7 × 0.20HE structure.

The reinforcing cord of the curve denoted by C has the same configuration as described above, but it is made of an elongated element obtained by winding the aforementioned strands on a textile yarn having 36 warp yarns twisted together. Therefore, it has the (36) +3 × 7 × 0.20HE configuration.

The reinforcing cord of the curve denoted by D has the same construction as described above, but it is made of an elongated element obtained by winding the aforementioned strands on a textile yarn having 54 warp yarns twisted together. Therefore, it has the (54) +3 × 7 × 0.20HE structure.

The reinforcing cord of the curve denoted by E has the same construction as described above, but it is made of an elongated element obtained by winding the aforementioned strands on a textile yarn having 72 warp yarns twisted together. Therefore, it has the (72) +3 × 7 × 0.20HE structure.

Fig. 9 shows that the metal reinforcing cords 10 manufactured according to the present invention all have a greater elongation at part load and elongation at break than the conventional HE metal reinforcing cord without decreasing the rigidity and load at break while maintaining the same stranding pitch, number of strands and number of wires per strand, diameter of wire, metal material and degree of preforming. It should also be noted that the part load elongation and elongation at break increase with increasing number (and diameter) of warp yarns of the textile yarns used.

The above discussed graph thus confirms what has been stated earlier, namely that by varying one or more of the number of

metal filaments

11, 11a, 11b, the diameter (or linear density) of textile yarns 20 (i.e. the number of filaments or ends of textile yarns 20), the stranding pitch P, the number of textile yarns 20, the degree of preforming in the stranding device 60 or the gumming machine, it is possible to manufacture metal reinforcing cords 10 having different helical geometries (or configurations), and therefore to manufacture metal reinforcing cords 10 each time having a mechanical behaviour which is considered most suitable for the tyre or structural part of interest.

As an example, fig. 10-19 show various metal reinforcing cords 10 made according to the present invention and corresponding conventional metal reinforcing cords, denoted STD. All of the illustrated reinforcement cords have a helical geometry, but such helical geometry differs depending on the particular configuration of each of the illustrated reinforcement cords.

On the left side of each of the illustrated reinforcing cords, various cross sections of the reinforcing cords are shown, and on the left side of these cross sections, a specific configuration of the metallic reinforcing cords is given. The twist pitch in mm is denoted by P, and the number of warp yarns of the textile yarns 20 used to make the illustrated metal reinforcing cord 10 is in brackets.

The reinforcing cords shown in fig. 10 are HE metal reinforcing cords, each comprising three metal strands, each comprising four HT steel wires having a diameter equal to 0.175mm, twisted together with a twisting pitch equal to 6.3mm

It should be noted that, as the configuration changes, the helical geometry of the metallic reinforcing cord 10 and the distribution of the metallic filaments in the predetermined piece of elastomeric material also changes. In particular, unlike conventional HE metal reinforcing cords in which the metal filaments (grouped into strands in this case) are collected together and substantially centred on the aforementioned sheet, in the metal reinforcing cord 10 made according to the invention the metal filaments (also grouped into strands) are distributed over a wider area of the aforementioned sheet as the diameter and the stranding pitch of the textile yarns increase.

On the other hand, the reinforcing cord shown in FIG. 11 comprises four HT steel wires with a diameter of 0.30 mm. The geometry of all these reinforcing cords is such that, in some or all of their cross-sections, at least some of the steel filaments are in a condition of substantial mutual contact (this expression means a condition in which two adjacent steel filaments are in actual contact and a condition in which the distance between two adjacent steel filaments is much less than the diameter of a steel filament, in particular equal to or less than half the diameter of a steel filament, even more in particular less than one third the diameter of a steel filament). The two metal reinforcing cords 10 have a space defined between the individual steel filaments and initially occupied by the textile yarns used to make them, which is much greater than that of conventional metal reinforcing cords. This space increases when the diameter of the textile yarn used increases (and thus when the number of filaments and/or warp yarns of the textile yarn increases), while keeping the other parameters unchanged. From the top to the bottom of fig. 11, the permeability, elongation at break and elongation at part load increase.

According to the present invention, it is possible to manufacture the metal reinforcing cord 10 with a spiral geometry such that in all its cross sections the metal filaments are in a state of substantial mutual contact, or to manufacture the metal reinforcing cord 10 with a spiral geometry such that in a first cross section of the metal reinforcing cord 10 some or all of the metal filaments are in a state of substantial mutual contact and in a second cross section of the metal reinforcing cord 10 some or all of the metal filaments are spaced apart from each other.

The invention also makes it possible to manufacture a metal reinforcing cord 10 having a helical geometry such that in all cross sections of the metal reinforcing cord 10 all the metal filaments are spaced apart from each other.

The pitch of the metal filaments can be obtained by suitably deforming (or preforming) the metallic reinforcing cord 10 while pulling the metallic reinforcing cord 10 with a predetermined traction force, which may be constant or varying over time. Such deformation (or preforming) can be obtained by passing the metal reinforcing cord 10 through a plurality of cylinders with reduced diameter, for example comprised between 1 and 5mm, at a predetermined tension. This deformation is the smallest when larger diameter cylinders are used, and the largest when smaller diameter cylinders are used.

Fig. 12 shows a conventional metal reinforcing cord (indicated with STD) and five metal reinforcing cords 10 made according to the invention, these metal reinforcing cords 10 being subjected to a suitable deformation so as to space all the metal filaments from each other. The reference "pref" (preformed) indicates the degree of deformation (minimum or maximum) to which the metallic reinforcing cord 10 has been subjected, so as to space all the metal filaments from each other.

All the reinforcing cords shown in fig. 12 comprise five UT steel filaments with a diameter equal to 0.22 mm.

It should be noted that, while keeping the other parameters constant, the helical geometry of the metallic reinforcing cord 10 and the distribution of the metal filaments in a predetermined sheet of elastomeric material vary as the stranding pitch P increases. In particular, unlike conventional metal reinforcing cords in which the metal filaments are collected together and substantially in the centre of the aforementioned sheet, in the metal reinforcing cord 10 the metal filaments are distributed over the entire volume of the aforementioned sheet.

It should also be noted that the greater the deformation, the greater the distribution of the wires over the entire volume of the piece of elastomeric material, while keeping the other parameters constant (comparison between the last two reinforcing cords at the bottom of fig. 12). Therefore, the degree of deformation imparted to the metal reinforcing cord 10 can also be considered as a useful parameter, according to which interventions are made to provide the metal reinforcing cord 10 with a helical geometry (and therefore mechanical behaviour) considered ideal for the specific application required.

The distribution of the metal filaments within the aforesaid structural components can be varied by varying over time the magnitude of the traction with which the metal reinforcing cord 10 is pulled during the aforesaid deformation or during the incorporation of the metal reinforcing cord 10 into the piece of elastomeric material to manufacture the structural component of interest of the tyre.

According to the invention, it is possible to manufacture very flat metal reinforcing cords 10, since it is possible to have a very large stranding pitch (for example equal to 35mm) without the risk of unraveling. This makes it possible to double (or more generally multiply) the number of metal reinforcing cords provided in a particular portion of the structural member sheet, relative to the case where conventional metal reinforcing cords are used.

Fig. 13 shows the HE metal reinforcement cord discussed with reference to fig. 9.

Fig. 14 shows four metal reinforcing cords 10 made according to the invention. To manufacture each of such metal reinforcing cords 10, two textile yarns are used, each yarn comprising 16 warp yarns twisted together (the first and third cords move from top to bottom in fig. 15) or 36 warp yarns twisted together (the second and fourth cords move from top to bottom in fig. 15). Two textile yarns are twisted together with four UT wires with a diameter equal to 0.30 mm. It should be noted that as the number of warp yarns and the twist pitch of the textile yarns increase, the wires tend to be aligned almost parallel. In this case, the part load elongation is low, but the machine output increases.

With reference to the metallic reinforcing cord 10 shown in fig. 15-19, similar considerations can be made regarding the correlation between the twist pitch and the machine output and/or the number of warp yarns of the textile yarns and the machine output. The first reinforcing cord shown in each of the preceding figures is a conventional metal reinforcing cord, denoted STD. The construction of each of the reinforcing cords shown in fig. 15-19 is clear from the indications given in the preceding figures and from the aforementioned reinforcing cords and examples discussed above.

The applicant has also made other examples of metal reinforcing cords 10 and compared the mechanical behaviour of these reinforcing cords with that of conventional HE metal reinforcing cords of similar construction. All these metallic reinforcing cords comprise three strands twisted together, each strand comprising seven metal wires having a diameter equal to 0.20mm (this metallic reinforcing cord thus having a 3 × 7 × 0.20HE construction). The strands are twisted together with a first twist pitch and the wires in each strand are twisted together with a second twist pitch. The comparative results are shown in table 1 below.

TABLE 1

In table 1, the first cord is a conventional metal reinforcing cord, while the other four cords are metal reinforcing cords 10 according to the invention, which differ from each other by the type of textile yarn used to make them.

In a conventional metallic reinforcing cord, the first stranding pitch is equal to 3.8 mm and the second stranding pitch is equal to 6.3 mm.

In the metal reinforcing cord 10 having the configuration 1+1 x (36) +3 x 7 x 0.20HE, a center textile yarn comprising 36 warp yarns and a crown textile yarn comprising 36 warp yarns are used. These two textile yarns are twisted together with the aforementioned metal wire strands. The first twisting pitch is equal to 3.15mm and the second twisting pitch is equal to 6.3 mm.

In the metal reinforcing cord 10 having the construction 1+2 x (36) +3 x 7 x 0.20HE, a central textile yarn comprising 36 warp yarns and two crown textile yarns each comprising 36 warp yarns are used. These three textile yarns are twisted together with the aforementioned metal wire strands. The first twisting pitch is equal to 4.2 mm and the second twisting pitch is equal to 12.5 mm.

In the metal reinforcing cord 10 having the configuration 1+3 × (36) +3 × 7 × 0.20HE, a central textile yarn comprising 36 warp yarns and three crown textile yarns each comprising 36 warp yarns are used. These four textile yarns are twisted together with the aforementioned metal wire strands. The first stranding pitch was equal to 4.2 millimeters and the second stranding pitch was equal to 12.5 millimeters.

It should be noted that some metal reinforcing cords 10 have an elongation at break greater (even much greater, see values of 12.4% and 14.58%) than that of conventional metal reinforcing cords, with substantially the same stiffness and breaking load.

The applicant has observed that the metal reinforcing cords usually used in tyre carcass structures do not allow a proper penetration of the surrounding elastomeric material due to their particularly closed geometry. In such reinforcing cords, the metal filaments are generally in contact with each other and therefore are subjected to undesirable fretting phenomena, compromising the structural integrity of the tyre.

On the other hand, the metal reinforcing cord 10 manufactured according to the present invention, thanks to the free space obtained by removing the textile yarns and the possibility of spacing the various metal filaments apart, allows sufficient penetration of the elastomeric material inside the cord and prevents mutual contact of the various metal filaments, while reaching values exceeding the breaking load, elongation at break and elongation at part load acceptable for the specific application. Thus, it is possible to use a smaller number of wires in the carcass structure, or, in the case of an equal number of wires, a wire having a smaller diameter to achieve the desired structural integrity of the tyre, with advantages in terms of weight and cost of the tyre.

All the examples discussed above and illustrated in the figures demonstrate how likely it is to be possible to manufacture, by means of the process and/or the apparatus of the invention, metal reinforcing cords 10 having different mechanical behaviour, so that each time the ideal metal reinforcing cord for a specific application can be identified. In particular, the reinforcing cord 10 may be used in the cross belt structure and/or in the chafer and/or in the flipper and/or in the zero-degree belt and/or in the chafer and/or in the flipper of a motorcycle tire.

In a particularly advantageous aspect thereof, in a preferred embodiment of the invention, the invention makes it possible to manufacture a metallic reinforcing cord 10 for tyres for cars and motorcycles, the metallic reinforcing cord 10 comprising at least two metallic wires twisted together with a predetermined twisting pitch and having a elongation at partial load greater than 3%, even more preferably greater than 3.5%, even more preferably greater than 4%, and/or preferably greater than 5%, more preferably less than 20%, even more preferably up to 12%, and/or wherein the twisting pitch P is preferably greater than 2mm, more preferably greater than 3mm, even more preferably greater than 4mm, even more preferably greater than 5 mm. Such reinforcing cords can also be used in tyre types and/or structural components of tyres in which conventional metal reinforcing cords cannot be used.

This is also the result of a series of comparative laboratory tests performed by the applicant. These tests show that the elongation at break and the elongation at part load of the metal reinforcing cord 10 manufactured according to the invention can reach values even far greater than those of corresponding conventional metal reinforcing cords.

All numerical ranges are in the following obtained taking into account all combinations of wire diameters and wire numbers, minimum diameters and minimum numbers of wires, maximum diameters and minimum numbers of wires, minimum diameters and maximum numbers of wires, maximum diameters and maximum numbers of wires.

The applicant has simulated the mechanical behaviour of a metallic reinforcing cord manufactured with the process described above with reference to figures 4, 5a and 5b, having an n × D configuration, i.e. comprising a plurality of wires twisted together, preferably with a single twisting pitch, where n is the number of such wires, preferably comprised between 2 and 6, for example equal to 2 or 3 or 4, D is the diameter of the wires, chosen from any of the values of diameter cited above, and preferably equal for all the wires of the metallic reinforcing cord. The applicant compared the mechanical behaviour of such a metallic reinforcing cord with that of a corresponding conventional metallic reinforcing cord of the same construction and measured elongation at break values ranging from 1.5% to 2.0% and elongation at partial load values ranging from 0.2% to 0.8% for the conventional metallic reinforcing cord, whereas for the metallic reinforcing cord manufactured with the above process the elongation at break values range from 1.5% to 15% and the elongation at partial load values range from 0.2% to 10%. According to the applicant, the metallic reinforcing cord 10 according to the present invention and having the aforesaid configuration has particularly preferred applications in the cross belt structure and/or in the chafer and/or in the flipper and/or in the zero-degree belt and/or in the flipper of a motorcycle tire.

The applicant has also simulated the mechanical behaviour of a metallic reinforcing cord made with the process described above with reference to fig. 4, 5a and 5b, having an n +1 xd or 1+ nxd configuration, i.e. comprising a strand of wires twisted together with a first twisting pitch, the strand being twisted together with a single wire with a second twisting pitch, which may be equal to or different from the first twisting pitch, preferably equal, where n is the number of wires in the strand, preferably between 1 and 6, for example equal to 1 or 2, D is the diameter of the wires, selected from any one of the above diameter values, preferably equal to the diameter of all the wires in the strand, not necessarily equal to the diameter of the single wire. The applicant compared the mechanical behaviour of such a metallic reinforcing cord with that of a corresponding conventional metallic reinforcing cord of the same construction and measured elongation at break values ranging from 1.3% to 1.8% and elongation at partial load values ranging from 0.2% to 0.7% for the conventional metallic reinforcing cord, whereas for the metallic reinforcing cord 10 manufactured with the above process the elongation at break values range from 1.3% to 10% and the elongation at partial load values range from 0.2% to 8.0%. According to the applicant, the metal reinforcing cord 10 according to the invention and having the aforesaid configuration has a particularly preferred application in the cross belt structure of an automobile tyre and/or in the chafer and/or in the flipper and/or in the zero-degree belt of a motorcycle tyre and/or in the chafer and/or in the flipper.

The applicant has also simulated the mechanical behaviour of a metallic reinforcing cord made with the method described above with reference to fig. 4, 5a and 5b, having an m + n × D configuration, i.e. comprising one wire stranded together with a first stranding pitch, the one wire being stranded together with a plurality of other wires with a second stranding pitch which may be equal to or different from (preferably equal to) the first stranding pitch, where m is the number of wires in the strand, preferably between 1 and 6, for example equal to 2 or 3 or 4, n is the number of other wires, preferably between 1 and 6, for example equal to 2 or 3, where D is the diameter of the wire, chosen from any of the above diameter values, preferably equal to the diameter of all the wires in the strand, and not necessarily equal to the diameter of the other wires. The applicant compared the mechanical behaviour of such a metallic reinforcing cord with that of a corresponding conventional metallic reinforcing cord of the same construction and measured elongation at break values ranging from 1.5% to 2.0% and elongation at partial load values ranging from 0.2% to 0.8% for the conventional metallic reinforcing cord, whereas for the metallic reinforcing cord manufactured with the above-mentioned method the elongation at break values range from 1.5% to 15% and the elongation at partial load values range from 0.2% to 10%. According to the applicant, the metal reinforcing cord 10 according to the invention and having the aforesaid configuration has a particularly preferred application in the cross belt structure of a car tyre and/or in the chafer and/or in the zero-degree belt of a motorcycle tyre and/or in the chafer.

The applicant has also simulated the mechanical behaviour of a metallic reinforcing cord, preferably of the HE type, made with the process described above with reference to fig. 4, 5a and 5b, and having an mxnxd configuration comprising a plurality of wires stranded together with a first stranding pitch, each strand comprising a plurality of wires stranded together with a second stranding pitch, which may be equal to or different from (preferably equal to) the first stranding pitch, wherein m is the number of strands, preferably comprised between 2 and 5, for example equal to 2 or 3 or 5, n is the number of wires per strand, preferably comprised between 2 and 7, and may be equal to or different from m, for example equal to 2 or 3 or 6 or 7, wherein D is the diameter of the wires, preferably equal to the diameter of all the wires of all the strands. The applicant compared the mechanical behaviour of such a metallic reinforcing cord with that of a corresponding conventional metallic reinforcing cord of the same construction and measured elongation at break values ranging from 2.0% to 4.5% and elongation at partial load values ranging from 1.0% to 2.5% for the conventional metallic reinforcing cord, whereas for the metallic reinforcing cord manufactured with the above process the elongation at break values range from 2.0% to 15% and the elongation at partial load values range from 1.0% to 7.0%. According to the applicant, the metal reinforcing cord 10 according to the present invention and having the aforesaid configuration has particularly preferred applications in the cross belt structure of a car tyre and/or in the chafer and/or in the flipper and/or in the zero-degree belt of a motorcycle tyre and/or in the chafer and/or in the flipper.

The applicant considers that in an automotive tire, it is particularly preferable to use a metal reinforcing cord 10 having an n × D or m × n × D configuration. The main advantages of using such reinforcing cords are the high penetration capacity of the elastomeric material between the various metal filaments, the high elongation at break and the consequent high rigidity and high elongation at partial load. These advantages yield performance benefits, as well as at high speeds. For applications in zero belt, it is also considered particularly preferred to use metal reinforcing cords 10 having an m × n × D configuration.

The applicant also believes that in motorcycle tyres it is particularly preferable to use metal reinforcing cords 10 having an n × D or m × n configuration. In this case, the main advantage provided by the use of such reinforcing cords is the high penetration capacity and the high elongation at part load of the elastomeric material between the various metal filaments, and consequently the high rigidity. These advantages yield benefits in terms of weight and performance. Such reinforcing cords have an elongation at break equal to that of conventional HE or preformed metal reinforcing cords, which provides the further advantage of increasing the output of the machine, with consequent economic and productive benefits.

In the preceding two paragraphs, the term "high" is not necessarily to be interpreted in absolute terms, but rather in relative terms with respect to the corresponding features of a conventional metal reinforcing cord having the same construction. Thus, for example, with reference to the part load elongation, it is considered to be high when it is higher than the corresponding conventional metal reinforcing cord.

The invention has been described with reference to certain preferred embodiments. Different modifications can be made to the above described embodiments while remaining within the scope of protection of the invention as defined by the following claims.

Claims

1. A metallic reinforcing cord (10) for tyres for vehicle wheels, comprising at least two metal wires (11, 11a, 11b) twisted together with a first twisting pitch (P), wherein said metallic reinforcing cord (10) has a partial load elongation greater than 3%.

2. The metal reinforcing cord (10) according to claim 1, wherein said part load elongation is greater than or equal to 3.5%.

3. Metal reinforcing cord (10) according to any one of claims 1 to 2, wherein said first twisting pitch (P) is greater than or equal to 1 mm.

4. A metal reinforcing cord (10) according to any one of the preceding claims, wherein said first twisting pitch (P) is greater than or equal to 3 mm.

5. A metal reinforcing cord (10) according to any one of the preceding claims, having an elongation at break greater than or equal to 4.5%.

6. A metal reinforcing cord (10) according to any one of the preceding claims, having an elongation at break greater than or equal to 6%.

7. A metal reinforcing cord (10) according to any one of the preceding claims, wherein said at least two metal wires comprise at least one first metal wire (11a) and at least one second metal wire (11b), said at least one first metal wire (11a) being substantially straight, said at least one second metal wire being wound on said at least one first metal wire (11a) with a winding pitch equal to a predetermined said first twisting pitch (P).

8. The metal reinforcing cord (10) according to any one of claims 1 to 6, wherein said at least two metal wires (11a, 11b) define at least one first strand of metal wires (11), wherein said at least one first strand of metal wires (11) is twisted together with at least one second wire (12) with a second twisting pitch (P1) equal to or different from said first twisting pitch (P).

9. The metal reinforcing cord (10) according to claim 8, wherein the number of wires of said at least one first strand of wires (11) is between 2 and 7.

10. Metal reinforcing cord (10) according to claim 8 or 9, wherein said at least one first strand of metal wires (11) is stranded together with a plurality of second metal wires (12).

11. A metal reinforcing cord (10) according to claim 10, wherein said second metal wires (12) number between 2 and 7.

12. The metal reinforcing cord (10) according to claim 10 or 11, wherein the number of wires of said at least one first strand of wires (11) is equal to or different from the number of said second wires (12).

13. Metallic reinforcing cord (10) according to any one of claims 10 to 12, wherein said second metal wires (12) define at least one second strand of metal wires (11) twisted together with a twisting pitch equal to or different from said first twisting pitch (P).

14. The metal reinforcing cord (10) according to any one of claims 8 to 14, wherein said metal filaments (11a, 11b) of said at least one first strand of metal filaments (11) have a diameter equal to or different from a diameter of said at least one second metal filament (12).

15. A metal reinforcing cord (10) according to any one of the preceding claims, wherein said at least two metal filaments (11, 11a, 11b) are spaced apart from each other in any cross section of said metal reinforcing cord (10).